The present invention relates to the production of electronic devices and is particularly concerned with a process for the fabrication of electronic devices employing a non-conductive polymer substrate, portions of which can be selectively rendered conductive by suitable chemical treatment.
The free-base form of polyaniline is electrically non-conductive. Protonic acid doping of polyaniline by reaction of polyaniline with a protonic acid HX where X is, for example, Cl, to produce electrically conductive polyaniline is known, for example, as disclosed in A. G. MacDiarmid, et al, Mol. Cryst. Liq. Cryst., 121, 173 (1985). Conductive polyaniline of this type has been employed in batteries, as disclosed in French Pat. No. 1,519,729.
However, if a film or bulk polymer of a material, such as polyaniline, is subjected to treatment in preselected regions, as by normal protonic acid treatment, to form doped conductive regions, for example, to form a conductive strip, such conductive regions or strip remains conductively stable only for a very short time, after which such conductive regions diffuse, causing the entire piece to have constant conductivity.
Further, base-type conductive polymers, as represented by the protonic acid-doped polyaniline class of conductive polymers, are unstable and degrade when exposed to water. Stability on contact with water is extremely rare in prior art conducting polymers, such as produced by treatment of polyaniline with protonic acids.
An object of the present invention is to enable the construction of polymeric electronic devices without the use of metals.
Another object of the invention is to provide a process for producing electronic devices on a non-conductive polymer substrate which can be selectively converted by suitable treatment to provide conductive portions which do not tend to diffuse.
Still another object is the provision of novel procedure for the production of electronic devices, as noted above, wherein the conductivity of the conducting portions of such devices does not degrade if the components of the device are exposed to water.